Final answer:
The Monroe Doctrine aimed to prevent European interference in the Western Hemisphere, with James Monroe declaring it in 1823, backed by Secretary of State John Quincy Adams. It was later expanded by Roosevelt's Corollary, which sanctioned U.S. intervention in Latin American nations.
Step-by-step explanation:
The primary purpose of the Monroe Doctrine was B) To prevent European nations from interfering in the Western Hemisphere. This doctrine was articulated in President James Monroe's annual message to Congress in 1823, as a principal cornerstone of U.S. foreign policy, under the advisement of Secretary of State John Quincy Adams. The policy warned European powers against further colonization and interference with independent nations in the Americas, asserting that any such actions would be considered a hostile act against the United States.
While the doctrine asserted American protection of Western Hemisphere nations, Roosevelt's Corollary to the Monroe Doctrine later established the right of the United States to intervene in Latin American affairs whenever necessary, particularly to stabilize the economic affairs of small states in the Caribbean and Central America. This extension was seen by many as a justification of American imperialism and an assertion of U.S. dominance in the region.